XnView has an "open with" feature, i.e., if you right-click on a file you can select "open" F3 or "edit" F4 to get the same effect as in Windows explorer "open" or "edit". For images this is rather boring, "open" in explorer on my box starts XnView, so when I am already in XnView I rarely need F3. It is possible to define additional "open with" programs in XnView for any file, e.g., a hex. viewer better than the XnView built-in hex. viewer.

Disadvantages, when you want to get rid of a bad "open with" idea XnView only offers to delete everything, back to only F3 and F4. An additional "open with" tool works for any file, you cannot define something only for, say, PNG. Recently I decided that I want an "open command prompt here" feature also within XnView. And after that worked as expected I modified it to open tweakpng for PNG, or a command prompt for everything else. Eventually I arrived at a script opening exiftool -k for ICC / MIE / XMP, or dcraw -i -v for camera raw.

If you want similar "open with" functions you can copy and edit the code shown below, save it in a tools folder, where you have exiftool / dcraw / tweakpng / etc., and define it as "open with" application in XnView. For the latter XnView first offers to open an *.exe, but it is a simple plain text *.cmd, you have to select * to see all files including *.cmd, not only *.exe and also not only *.bat. The name doesn't matter, I use OPENDIR.cmd: